It has become common practice to transport cargo by way of a trailer which is towed behind a motor vehicle, such as a car or a truck. Due to the hazards associated with this means of transporting cargo, most states have adopted provisions, as part of their vehicle codes, which govern the methods and hardware used in connection with such towing. In addition, voluntary organizations, such as the Society of Automotive Engineers (SAE), and equipment manufacturers have adopted standards for improving the safety of towing cargo.
The most common type of trailer hitch in use today is composed of two basic components: a ball member mounted to the rear of the towing vehicle, and a mating socket member connected to the forward end of the towed trailer. Once the socket has been placed or seated on the ball member, a latch mechanism is actuated to securely couple the two together. Once the latch mechanism is actuated or closed in this manner, the socket will not become separated from the ball member. In addition to the primary attachment described, an electrical connection is usually made between the towing vehicle and the trailer to allow brake lights, turn signals, etc., mounted on the trailer to be activated from the towing vehicle. The ball and socket coupling, when attached together, provides maneuverability between the trailer and the towing vehicle to accommodate turning and uneven terrain.
Trailer hitches of this sort can fail for a number of reasons. Perhaps the most common causes of failure all relate, in one way or another, to the latch mechanism. These include failure of the latching mechanism, failure of the operator to properly actuate the latching mechanism, or failure of the operator to latch the coupling at all. As noted, if the latch is not properly secured or becomes open during transit the ball/socket coupling is subject to failure. Failure of the coupling can result in the separation of the trailer from the towing vehicle, usually with no warning to the operator, which can be extremely dangerous, resulting in the loss of a life and/or a valuable trailer and its cargo.
Certain trailers, particularly those of larger size, have electrically activated brakes which can be operated by the driver once electrical connection is made with the towing vehicle. The trailer brakes are activated simultaneously with the brakes on the towing vehicle and are controlled by the brake pedal. However, the braking force applied by the electrical trailer brakes is not dependent on the force applied to the brake pedal of the towing vehicle. Rather, the trailer brakes are either "on" or "off", but the level of braking force applied when they are turned "on" may be set manually, using a rheostat or similar control device, to be a set proportion of the total possible braking force of the trailer brakes. In this manner, the operator may adjust the braking force of the trailer brakes for varying loads.
In addition, the vehicle codes of most states require certain trailers to have safety braking systems, which are powered when the trailer becomes separated from the towing vehicle and electrical connection between the trailer and towing vehicle is broken. In most cases, these safety braking systems are powered by stand-by batteries located on the trailer as is described in greater detail below. Likewise, due to the frequency and severity of accidents resulting from separation of a trailer hitch coupling, most state vehicle codes require the use of safety chains to maintain connection between the trailer and the towing vehicle in the event of an uncoupling of the trailer hitch. While safety chains provide an added measure of protection, it is hard to control a trailer which is being towed only by chains, and accidents are common even when safety chains are used. Moreover, safety chains frequently break. For trailers having electrical brakes, there is normally a safety pull cable which is released after the chains break to activate the trailer brakes.
As described, a typical trailer with brakes has four connections with the towing vehicle: the primary ball/socket connection; the electrical connection for transmitting electrical signals to the trailer's brake lights, turn signals, brakes, etc.; safety chains connecting the trailer to the towing vehicle as a back-up safety system; and a breakaway cord attached to a switch to activate the trailer brakes. The breakaway cord is a pull-cable, longer than the safety chains, which is connected to an electrical switch controlling the trailer's electrical brakes. Ideally, if the ball and socket connection fails, the chains will prevent the trailer from disengaging entirely from the towing vehicle. However, if the chains break, then the breakaway cord is pulled, and the trailer brakes, typically powered by a twelve volt auxiliary dry cell battery on the trailer, are engaged to stop the trailer. The prior art devices rely on this braking system to slow the trailer to a stop; however, the unfortunate reality is that the battery on the trailer which controls the brakes is often dead or discharged, and therefore the brakes do not function in the intended manner in an emergency. Since the battery on board the trailer used to power the brakes is there solely for emergency purposes, trailer owners quite often neglect to periodically replace it.
The prior art describes various safety devices designed to detect the uncoupling of the trailer hitch and to alert the operator. Examples of prior art safety devices are described in Engle, U.S. Pat. No. 4,593,264; Gehman, et al., U.S. Pat. No. 4,627,633; and Ellis, et al., U.S. Pat. No. 3,792,432. The devices shown in these patents have the objective of warning the operator, usually by sounding an alarm, when the coupling has disengaged. Nonetheless, there are drawbacks to each of the devices shown. These devices are also limited in their usefulness, in that none of them prevent the coupling failure in the first place.
All of the prior art devices known to the inventors are activated only when the socket member actually separates from the ball member. Some of the devices in the aforementioned patents have specially designed, non-standard ball members with an electrical switch inside the ball, which is activated when the ball and socket separate. Other devices have an external switch activated by the socket member lifting off of the ball member. Thus, these devices will not warn the operator if the coupling is not secure, for example, if the latch has not been properly closed. Also, these prior art devices will not detect an unlatched coupler until the trailer has separated from the towing vehicle, which may be too late to prevent an accident.
Known prior art trailer hitch safety devices are mounted on the towing vehicle, rather than the trailer. Accordingly, if another towing vehicle lacking the specialized apparatus shown in the patent is used to tow the trailer, there will be no safety system present. Thus, the valuable cargo which may have prompted the purchase of the safety device may be unprotected if any other towing vehicle is used. It is noted that the use of different towing vehicles is common.
Known prior art devices also do not prevent the movement of an improperly secured trailer. All of the devices in the aforementioned patents merely warn the operator that the trailer is not coupled to the towing vehicle; none of them apply the trailer brakes to prevent the trailer from being towed when the coupling is not secured.
With these deficiencies of the prior art in mind, it is an object of the present invention to detect and notify the operator when the latching mechanism of a trailer hitch is not properly engaged.
It is also an object of this invention to notify the operator when the latching mechanism of the socket member becomes disengaged while being used, so that warning is given before the hitch becomes uncoupled.
Another object of the present invention is to activate the trailer brakes, using power from the towing vehicle, when the latching mechanism is not properly engaged, so that the trailer is prevented from moving if the connection is not secure.
Yet another object of the present invention is to activate the trailer brakes after a predetermined time period whenever the coupling fails while the trailer is being towed to stop the trailer as well as the towing vehicle.
It is also an object of the present invention to position the safety system of the present invention on the trailer, such that the trailer is protected regardless of the vehicle being used to tow it.